The present invention relates to electro-optical circuits, and specifically, to a circuit board for optically interconnecting a plurality of electro-optical micro circuits.
With the development of medium and large scale integration of logic circuit elements used in data processing systems, the problem of interconnecting the logic elements becomes increasingly difficult to solve. Conventional electrical connection means such as printed circuit boards have become relatively complex and therefore costly. The inherent two-dimensional limitation imposed by the use of only the surfaces of printed circuit boards, severely limits the flexibility of such boards for interconnecting a plurality of integrated circuit devices even when both sides of the board are used.
Another difficulty with the interconnection of various logic circuit elements in an electrically connected circuit board is the reliability of solder joints or wire wrap joints when used. This is particularly acute where "plated-through holes" are used in multi-layer boards. Also, where many solder joints are required, the possibility of damage associated with replacing defective micro-circuits soldered into the printed circuit board is increased greatly when technicians are required to unsolder and disconnect each of the circuits.
Another difficulty is that with conventional electrically coupled micro-circuits, the servicing and troubleshooting to isolate faulty components within a circuit board containing a plurality of such devices requires a highly skilled technician and complicated and relatively expensive test equipment. The optical circuit board of the present invention which optically connects the electrical optical micro-circuits, provides readily-visible optical terminals which will be illuminated in a predetermined manner thereby providing information as to the operability of micro-circuits within the circuit board. Such a system greatly simplifies the troubleshooting and does not require complicated or expensive test equipment.
Another problem with electrically conductive circuit boards conventionally used to interconnect micro-circuits is one of crosstalk caused by inductive couplings between adjacent conductors. The optical circuit paths employed with the apparatus of the present invention constrains the light transmission to optical fiber paths and no crosstalk problem exists. Also, the micro-circuit devices and optical conductors are preferably placed between a pair of conductive plates which serve as shields, effectively shielding the circuits from external noise or other electrical interference.
Finally, in conventional circuit boards, heat is removed from individual integrated circuits by conduction from only one major surface of each of the integrated circuits. In the apparatus of the present invention, however, both surfaces of each of the micro-circuits are in thermal communication with heat conducting surfaces thereby greatly increasing the flow of heat generated within the device away from the micro-circuits.
With the advent of fiber optic technology, some attempt has been made to provide optical interconnections between electrical devices as well as to provide optical logic circuits. U.S. Pat. No. 2,833,936, T. I. Ress, issued May 6, 1958; U.S. Pat. No. 3,423,594, A. G. Galopin, issued Jan. 21, 1969; and U.S. Pat. No. 3,519,116, R. Koehn, issued July 7, 1970 represent some efforts made to employ fiber optics, or other light conductive paths to produce either optical digital circuits or to couple optical fibers to conventional photo electric components. None of these patents suggest, however, the interconnection of a pllurality of micro-circuits by means of a circuit board structure including optical sockets therein adapted to receive microcircuit device wafers, as does the present invention.